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Thursday, November 24, 2011

Jeff Masters: A strange 2011 Eastern Pacific hurricane season

A strange 2011 Eastern Pacific hurricane season

by Jeff Masters, wunderblog, November 24, 2011

The Eastern Pacific's late season surprise, Hurricane Kenneth, is falling apart nearly as fast as it intensified. Kenneth, now a Category 1 hurricane with 90 mph winds, was a powerful Category 4 storm with 145 mph winds yesterday, and was by far the strongest hurricane to appear so late in the year in either the Eastern Pacific or Atlantic Oceans. Kenneth is moving over colder water and into a region with higher wind shear, and will continue to deteriorate over the next few days. Kenneth is not a threat to any land areas.

Figure 1. GOES-West satellite image of Hurricane Kenneth taken at 11 am EST November 22, 2011. Image credit:NOAA Visualization Lab.

The 2011 Eastern Pacific hurricane season: a strange one
Hurricane season officially ends next week on November 30 in both the Atlantic and Pacific Oceans, and it is likely that we won't see any more named storms in either basin. It was a strange hurricane season in the Eastern Pacific, but in the opposite sense of the Atlantic's strange season. The 2011 Eastern Pacific hurricane season featured a well below-average number of named storms--eleven (fifteen is average). However, all but one of these storms reached hurricane strength, the highest proportion of hurricanes in a single season ever recorded. Six of the hurricanes became intense hurricanes, double the normal. An average Eastern Pacific hurricane season has 15 named storms, 8 hurricanes, and 3 intense hurricanes. It is common for an Eastern Pacific hurricane season to have fewer named storms than usual during a La Niña year, like this year. It is unusual to have so many hurricanes and intense hurricanes in a La Niña year. The only La Niña years to record so many intense hurricanes in the Eastern Pacific were 1971 and 1985 (six and eight intense hurricanes, respectively.) The strongest Eastern Pacific storm of 2011 was Hurricane Dora, which topped out as a Category 4 hurricane with 155 mph winds. The deadliest cyclone was Tropical Depression 12-E, which made landfall near the Mexico/El Salvador border on October 13. At least 105 people died in Central America due to TD 12-E's flooding rains. El Salvador recorded an astonishing 1.51 meters (4.96') of rain in a ten-day period due to TD 12-E and its remnants.

Figure 2. Tracks from the 2011 Eastern Pacific hurricane season.

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